Aerological instrument



April 18, 1939. c. P. YAGLOU, 2,154,927

AEROLOGICAL INSTRUMENT Filed June 28; 1935 INVENTOR. Co/vsr/wmv P )haou A TTORNEY.

Patented Apr. 18, 1939 UNITED STATES PATENT OFFICE.

3 Claims.

This invention relates to air conditioning, and more particularly, to apparatus'for measuring and controlling factors affecting human comfort.

Approximately eighty per cent of the body surface of the average person, when conventionally attired, is covered by an aerial envelope formed between the skin and the outer clothing. The temperature of this aerial envelope increases progressively from about 84 degrees F. between the outer two layers of clothing, to about 96 degrees F. at the surface of the skin under the clothing. In order that a person may feel comfortable, it is essential that the temperature of this aerial envelope-remain substantially constant in summer and winter. When the temperature of this envelope drops appreciably, the sensation of cold is experienced, and when it rises, the sensation of warmth is experienced." The temperature of this aerial envelope is dependent upon heat transfer between the body and its surroundings. When heat is dissipated .from the body at a rate equal to that at which it is generated by the metabolic processes, the temperature of the air space between the outer two layers of clothing approximates 84 degrees F., and the individual will feel comfortable.

The dissipation of bodily heat is effected mainly by radiation and convection. Evaporation is usually a minor factor, although when the air is uncomfortably warm, it plays an important emergency cooling role. The rate of heat loss by radiation depends entirely upon the difference between the temperature of the body surface and the mean surface temperature of the surrounding walls and objects. The'rate of heat loss by convection depends upon the temperature difference between the body and the surrounding air, and upon the rate of air motion over the body. The loss by evaporation is largely dependent upon sweat gland activity, relative humidity, and air movement. The sweat gland activity, in turn, is controlled by external temperature and the degree of physical activity.

The conventional dry bulb thermometer does not provide a true index of warmth or of the temperature of the aerial envelope surrounding the body, for it is substantially unaffected by radiant heat, while the temperature of the aerial envelope is affected greatly by radiant heat. Thus, a person in a room in which there are relatively cold walls and windows may feel cold, although the air in the room is at 70 degrees, due to radiation of heat from his body to the'cold walls and windows. Conversely, a person in a room in which the thermometer indicates a temperature of 60 degrees may feel entirely comfortable, or even uncomfortably warm, if he is subjected to the radiant heat rays of the sun, a radiator, or other warm object. The standard dry bulb thermometer is not at all affected by air motion, and

thus fails to indicate accurately the extent to which the body is cooled by convection. The effective temperature index also fails to indicate accurately the summated effect of radiation and convection on the temperature of the aerial envelope surrounding the body because it does not take into account the effect of radiation and because it underestimates the effect of convectional currents of low velocity.

In the past, there have been devised instruments of various types for the purpose of ascertaining the relative comfort of various environ-- ments, and for studying the effectiveness of different methods of heating, ventilating and air conditioning. All of the instruments heretofore in use have more or less serious limitations in principle and design, and are far from satisfactory. The best of them are needlessly complicated and expensive; and their readings are in such form as to require interpretation.

Among the instruments which have been used in the past are the eupatheoscope and the eupatheostat. Both of these instruments operate on the basis of a variable heat input and constant surface temperature. In the case of the human body, and in the case of applicant's instrument, however, the reverse holds true, i. e., the metabolism or heat input remains constant within the comfort zone, but the surface temperature of clothing and the aerial envelope temperature vary according to external conditions. In operation, the eupatheoscope and eupatheostat either overcompensate or undercompensate for radiation and convection. For example, let us assume that a certain environment lowers the surface and aerial envelope temperature of the body two degrees. Heat loss from the body will then take place at a temperature two degrees lower than the surface temperature of the eupatheoscope, because the surface temperature of this instrument is automatically kept constant regardless of the variations in external conditions. Since the heat loss by radiation varies as the fourth power of the absolute temperature of the radiating source, considerably more heat will be lost from the eupatheoscope than from the human body under identical external conditions, and if a eupatheostat is used to control the room temperature, it is apt to. cause overheating. The error is in the opposite direction in warm environments.

Furthermore, the eupatheoscope and.eupatheostat require measurement and control of surface temperatures. This procedure is complicated and expensive, requiring the use of involved auxiliary equipment. Moreover, these instruments cannot be used to advantage in practical installations in the air conditioning field, being outside the scope of the layman.' Further,

, square foot per hour,

It is another object of the invention to provide apparatus for controlling atmospheric conditions in an enclosure responsive to variations in the summated effect of radiation, convection and evaporation on the comfort of human beings within the enclosure.

It is another object of the invention to provide an improved anemometer.

It is another object of the invention to provide a novel comfort meter which is relatively simple, inexpensive and accurate.

In an elementary form, applicant's apparatus comprises two hollow metal or cloth spheres, one inside the other. Heat generated by a heating element withinthe inner sphere is dissipated by the outer sphere at the rate of 15.3 B. t. u. per

under standard environmental conditions (air and walls at '70 degrees F., with substantially no air motion). This is approximately the average rate of heat loss from the surface of an average adult person by radiation and convection under comfortable air conditions. One or more thermometers are positioned in the air space between the spheres, to register the temperature thereof. The outer surface of the inner sphere is then comparable to'the human skin.. The air space between the two spheres is comparable to the aerial envelope between the skin and the outer clothing, and the thermometers register the temperature between the outer two layers of clothing. The apparatus is subject to radiation and convection effects in approximately the same way as a human body in the same position would be affected. Radiation and convection affect the temperature of the air space between the spheres approximately in the same way as they would affect the temperature of the aerial envelope between the skin and the outer surface of the clothing. In warm summer weather, when perspiration often occurs, the outer sphere is wetted, and the air between the spheres is cooled by evaporation to an extent depending upon the relative humidity and air movement.

Under such conditions, the instrument is made to dissipate heat at the rate of 20.5 B. t. u. per square foot per hour, by adjusting the resistance of the heating element. This rate of heat dissipation represents the total heat loss from the human body when at rest, by radiation, convection and evaporation.

Thus, applicant provides an apparatus which substantially reproduces the thermodynamic functions of the human body, and which is affected by external conditions in substantially the same way as the human body is affected by them.

A feature of the invention resides in the provision of a thermoresponsive element or elements within the air space betwen two containers for controlling atmospheric conditions externally of the apparatus responsive to variations in the temperature of said air space.

A further feature of the invention resides in the provision of a simple means for measuring air velocities.

Other objects and features of the invention will be more apparent from 'a consideration of the following specification, to be read in connec-: tion with the accompanying drawing, in which Fig. 1 is a cross-sectional view of one embodi ment of the invention;

Fig. 2 is a longitudinal section through another form of the invention in which cylinders are substituted for the spheres of Fig. 1;

Fig. 3 represents a section on the line 3-4 of Fi 2;

Fig. 4 illustrates the application of the invention to the control of heating means;

Fig. 5 illustrates a modified form of the invention; and

Fig. 6 diagrammatically illustrates the application of the invention to the control of remote indicating means. Referring to the drawing, a sphere III is posie tioned within a somewhat larger sphere H. These spheres may be of heat conducting material, such as copper or aluminum, or may be made of cloth fabrics on wire frames. The outer sphere is preferably blackened, on the outside. A heating element I2 is positioned within sphere l0. Element I2 is preferably a variable electrical resistance, supplied with electrical current from any suitable source through leads H, which are carried through and insulated from spheres l0 and H by conduit II, which also retains the spheres in spaced relation. Thermometers I! are positioned in the air space l6 between the spheres to register the temperature thereof. The stems of the thermometers l5 are preferably car- 'ried by small air tight conduits 25 extending through sphere ll. Instead of glass thermometers, thermocouples or resistance thermometers may be used for automatic registration of temperature or control thereof.

Applicant prefers to standard 4 ball cock, and as the outer sphere II a standard 6" ball cock. The heating element I! has two graduated stops at b and 0. Section ab has a resistance of 2010 ohms, and section ac, a resistance of 3440 ohms. The contact point if is normally at 0, except when the "outer sphere is wetted in hot weather, when conutilize as the sphere! a ta'ct d is moved to b. When heating section ac is connected to a current source of 110 volts, the heat loss from the outer sphere approximates 15.3 B. t. u. per square foot per hour, the average rate at which heat is dissipated from the body surface of an adult by radiation and convection under comfortable conditions. When heating section ab is connected to an electrical source of 110 volts, the heat loss from the outer spheres is at the rate of 20.5 B. t. u. per square foot per hour, the average rate at which is dissipated from the body of an adult by radiation, convection and evaporation. It is apparent that spheres of other sizes" may be used in conjunction with suitable heating elements without departing from the spirit of the invention.

Under standard environmental conditions, the average temperature between the outer two layers of clothing and from the exposed skin surfaces of the head and hands varies between 82 and 86 degrees. The air between the outer two layers of clothing is most sensitive to and its temperature is .most indicative of changes in atmospheric conditions affecting human comfort. It may be assumed that under standard conditions of comfort, the temperature of this air space will be approximately 84 degrees. Therefore, thermometers I5 are so positioned within air space l6 that, when the apparatus is subjected to standard environmental conditions,

"they register 84 degrees.

In the triple globe thermometer illustrated in Fig. 5, thermometers I5 are so positioned in the air space I611 as to register 84 degrees when the apparatus is subjected to standard environmental conditions.

The thermometers l5 usually give identical vary in response to the same changes in radia Heated globe thermometer temperature in relation to sensations of warmth one of the thermometers, a drop in the temperature indicated by the thermometer will result from the greater heat transfer by convection from the outer sphere, due to the increased velocity of air passing in contact therewith. For studying the directional effects of radiant energy and air motion, it may be desirable to use additional thermometers, such as 15a, to give readings at points '90 degrees apart.

The temperature of air space It and the surface temperature of sphere I I are affected by the temperature of the air surrounding the apparatus, by radiation and by air movement. However, these temperatures are not affected by the humidity of the atmosphere surrounding the apparatus. At high temperatures, when the body is covered with perspiration, the amount of cooling due to evaporation is considerable. In such cases, accurate reflection of conditions by the thermometers may be assured by covering the outer sphere with a tight-fitting moist cloth I! dipping in a pan l8 containing water and by decreasing the resistance of the heating element a as above described. It is to be understood, of

. Mean Glass ther- Apphmometer cants 2 5; $33,223: Sensation of warmth Conditions of exposure temperature device temperature Sitting near window, 2 from cold glass. Window shut. No sun- 70. 7 I 78 9 8.2 64. 9 Cold and drafty.

shine, radiator oil. Room heated and ventilated mechanically. 6" above floor level, close to feet of observer 67 3 74 6 3 60. 6 Cold feet and drafty. Sitting 8 away from a 10 desk fan 82- 3 5. 2 68. 3 Cool to cold.

Center of expt. room, 7 subjects, airflow 210 c. t. m. 74. 4 85. 8 11.4 71. 8 Very comfortable. Center of room, window open 1', door open 74. 5 85. 5 ll. 0 7l. 5 Do. 9' from a wood fire in front of a fireplace 67 2 85. 3 7- 7 Y 71. 3 Most comfortable and p easing. Outdoors in clear sunshine. Snow on ground. Mild breeze (75 45.0 84 2 39. 2 70 2 Body perfectly com- 00/min.). fortable. Feet cold.

Sitting in sunshine by window sill of espt'lroom. Window closed, 73. 9 87. 7 l3. 8 73. 7 Warm.

radiator o 6' from a wood fire in front of fireplace 2- 0 95. 0 23.0 80.0 Tonya/rm; slight perspire 1011.

Thus, in the presence of radiant heat, sun rays or air movement, the temperature registered by the conventional thermometer bears little or no relation to the sensation of warmth or cold experienced by the observers. On the other hand, the readings of the globe thermometer correspondvery well with sensations of comfort. Regardless of variations in air movement or radiant energy, the globe thermometer registered between 82 and 86 degrees, approximately, when conditions were comfortable. When cold was experienced, the globe thermometer registered below 82 degrees, and when the sensation of warmth was experienced, the globe thermometer registered 86 degrees or more.

Column 5 of the table gives the mean radiation-convection temperature of the environment. This is the temperature which an ordinary thermometer would register if it were possible for it to indicate the integrated effect of air temperature, positive radiation and convection, less that of negative radiation and convection. The readings of column 5 are obtained by subtracting 14 degrees from the readings of the applicant's device. The value of 14 degrees represents the difference between 84 degrees and 70 degrees, or the excess of globe temperature over air temperature in still air at 70 degrees with the walls and air at the same temperature. When the readings of the globe thermometer are transformed by subtraction of this factor, it will be seen that, as

indicated in column 5, comfortable temperatures fall between 70 and 72 degrees. cold ones under 68 degrees, and warm ones over '72 degrees. These values are well in accord with American standards of comfort. If desired, of course, the scales of the thermometers l5 may be so calibrated that they reflect temperatures of applicant's device corrected by subtraction of the 14 degree factor to read directly in familiar terms. Thus, there will be no need to interpret the readings of thermometers l5 and no need to depart from the layexample, operate valve 26 to control the admisby the direction from which aircurrents or radiant energy reach the cylinder, since the projected area of the cylinder is not the same in all directions, as in the case of the sphere. Hence, the cylindrical form of the invention is not as satisfactory as the spherical apparatus for measuring radiation or air movement. Vertical mounting is preferred.

Applicants apparatus may be utilized for controlling the temperature of an enclosure as indicated in Fig. 4. The thermoresponsive element is is positioned in air space IS in precisely the same manner as thermometers l5. Element l9 responds to variations in temperature in the air space l6, and through suitable control apparatus of any desired type, as indicated at 20, may, for

sion of steam through pipe 21 to the radiator 28 heating the enclosure. While applicant illustrates his invention as controlling the admission of steam to a radiator, the invention is adapted to be used in conjunction with air conditioning systems of any desired type. For example, applicants apparatus might be utilized to control the amount of conditioned air admitted to a conditioned enclosure, the admission of air to or the bypassing of air around an air washer, the temperature and supply of a heating or cooling agent, etc.

Since there are well-known'various forms of apparatus including thermo-responsive elements and means remote from said elements for indicating the temperature affecting said elements or for controlling valves, dampers or the like, for controlling the temperature or other characteristic of the atmosphere affecting said elements, no detailed description or illustration of such arrangements is deemed required here, it being understood that any of these arrangements may be used in conjunction with the thermo-responsive element of applicant's apparatus as herein described. One of these well-known remote indicating and/or controlling systems, for example, is the Fullscope" apparatus manufactured and widely marketed by the Taylor Instrument Company. Brown Instrument Company and other manufacturers also manufacture and widely sell such apparatus. Fig. 6 illustrates the application of the invention to the control of such remote indicating means. Thermo-responsive element lib is positioned between containers in and II and, through a suitable control line 29 of any desired type (as, for example, a pressuretransmitting tube), controls remote indicating means 30.

In addition to use as a comfort indicator, the heated globe provides a highly satisfactory means of measuring air velocities, particularly low air velocities, for the measurement of which no satisfactory instrument has been available heretofore. The operation of the apparatus as an anemometer is based upon the principle that as the velocity of air contacting the apparatus increases, the globe temperature tends to fall, due

to increased heat loss by convection. The relation between temperature of the globe and air velocity is expressed by the formula:

tgs tg KW where tgs=temperature of globe in still air. tg=globe temperature in moving air. 7 K=calibration constant.

V=air velocity in feet per minute. The globe temperature in still air (tgs) is given by the equation tgs=a+bta where a and b=instrumental constants and ta=air temperature.

When used as an anemometer, the outer sphere is preferably one to three inches in diameter and plated with cadmium to eliminate as much as possible the influence of radiant heat.

The heat input to the globe anemometer is varied according to the desired sensitivity and velocity of air to be measured. The higher the sensitivity and the higher the air velocity, the greater the heat input. By means of such an instrument, it is possible to measure air velocities within a fraction of a foot per minute by simply recording the temperature of the air and the temperature of the globe. To insure accurate air velocity determinations, care should be exercised to keep the apparatus at least 10 feet from radiators, cold walls, or the like. If this is not possible, the air velocity may be computed from the heat balance equation of the instrument, given below.

As heretofore described, the apparatus may be used to indicate the summated effect of radiation and convection. Often, however, it is necessary in problems of air conditioning to separate radi-- ation from convection and to estimate the effect of each of the factors involved, such as air temperature, air movement, mean radiation intensity, and the mean temperature of the surrounding surfaces. The heated globe affords a suitable means for determining these factors in"ividually. The heat balance equation of a 6" blackened globe may be written as follows:

The first expression on the right of the equatio represents the heat loss by radiation from the surface of the globe according to the Boltzman Stefan law. The second expression represents the heat loss by convection. The sum of the two is always equal to the heat equivalent of the electrical input to the globe (12.0 B. t. 11. per hour) regardless of environmental conditions.

This heat balance equation finds many practical applications in problems dealing with comfort under various conditions of air temperature, radiation, and air velocity. For example, it may be required to find the air temperature necessary to produce comfort in rooms in which the mean radiation temperature (Te) of the surrounding walls, glass, ceiling and floor is considerably above or below the usual values. Te may be computed from data given in the Guide of the American Society of Heating and Ventilating Engineers.

Ts=c+d (ta+4'60) where c and d are instrumental constants expressing the relationship between to and Ts.

For a double globe 6" in diameter o=50.4 and The value of tg for comfort is 84.0 (see table).

For still air, V may be taken as 10 feet per minute, or it may be determined by the use of a globe anemometer. The equation is then solved for to by substituting the values of the known factors.

In rooms heated by radiant methods, it is necessary to know the mean radiant temperature Te to which the surrounding surfaces must be warmed in order to produce a comfortable condition at any desired temperature and air movement. The values of to and Ts are as in the previous example. By substituting the desired values of to and V, the equation is solved for the unknown factor Te.

Knowing Te, the mean radiation intensity from the surrounding surfaces is:

The apparatus may also be used to determine the air velocity necessary to counteract radiant heat from furnaces or hot objects so as to produce a comfortable condition without sweating.

The instrument is particularly suitable for the study of drafts which are related to globe thermometer readings ta, or its equivalent ts.

A cylindrical globe is particularly suitable for studying the heat insulating qualities of fabrics under practical conditions. The difierence in the globe temperature readings with and without the cloth covering gives a direct measure of the insulation aflo'rded'by various types of clothing a under various conditions of temperature, humidity, wind, radiation, etc.

In the practical use of the globe thermometer as a comfort meter or as an anemometer, records of comfort and/or air velocity may be obtained at any distance away from the instrument by utilizing thermocouples instead of the glass thermometer inside the globe and carrying the wires to registering or recording mechanism (galvanometer, potentiometer, etc.) at any convenient point. Such applications are particularly useful in theatres, and large public and industrial buildings where the air conditions are controlled from a remote central room.

Since certain changes in the invention may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In an apparatus of the character described, a plurality of containers of diiferent sizes, said containers being nested within each other in spaced relationship, means for heating the smallest of said containers, and means for measuring the temperature between two of said containers.

2. In an apparatus of the character described, a first hollow container, a second hollow container positioned within and spaced from said first container, means for heating said second container, and thermo-responsive means between said first container and said second container.

3.. In an apparatus of the character described, a first hollow container, a second hollow container positioned within and spaced from said first container, means for heating said second container, thermo-responsive means between said first container and said second container, and

means for wetting the exterior surface of said first container.

CONSTANTIN P. YAGLOU. 

